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(1)

Architecture

(2)

Sensor Node Architecture

Battery

DC-DC

Sensor

ADC MCU

Memory

Radio

(3)

Available Devices

• MicaZ (Crossbow)

• 2.94 GHz IEEE 802.15.4 Zigbee radio

• 128 KB program memory

• 512 KB data memory

• 8 mA draw

(4)

Available Devices

• Tmote Sky/invent (Moteiv)

• 2.94 GHz IEEE 802.15.4 Zigbee radio

• 8MHz processor

• 10 KB RAM

• 48 KB Flash

(5)

Available Devices

• Stargate (Crossbow)

• Wired Ethernet

• Wifi/Cellular via PCMCIA

• INTEL PXA 255

• Linux Kernel

Environmental Monitoring Application Note

Data Interval (minutes)

Average MICA2 or MICA2DOT Current

(µA)

1 677

3 315

6 196

The XMesh network has been extensively tested both at indoor and outdoor locations. In a typical indoor test, nodes were placed at every 300 sq ft. to cover a 10,000 sq ft facility. To simulate larger distance between nodes, the radio transmit power was turned down to -6dBm. In outdoor tests nodes were spread across several acres of rugged terrain with an average density of 1 mote per 10,000 sq ft and at full radio power. Statistical analysis across many deployments shows on average greater than 90% of all traffic generated at any node will be collected at the base station without the use of end-end acknowledgements.

Stargate Base Station

Figure 4. Stargate gateway as a base station

The Crossbow Stargate gateway and microserver is an embedded Linux computer designed to be the primary access point for wireless sensor networks. The Stargate’s small form factor,

reliability, and optional communication interfaces makes it ideal for remote, environmental monitoring. A base station mote (MICA2) is connected to the 51-pin connector on the Stargate.

A resident program, XListen, takes an input stream of wireless sensor data from the base station mote and stores it in a local Postgres database.

The Crossbow Stagate can be connected to a wide-area or back-haul network in one of the following ways:

! Wired Ethernet connection

! WiFi, using a Compact Flash card (Netgear MA701, AmbicomWL1100C-CF, etc.)

(6)

Sensors

• Exterioceptors: information about the surroundings

• Proprioceptors: information about the

internal workings

(7)

Sensors

Measurand Transduction

Physical Pressure Piezoresistive, capacitive

Temperature Thermistor,

thermomechanical, thermocouple

Humidity Resistive, capacitive

Flow Pressure change, thermistor

(8)

Sensors

Measurand Transduction

Motion Position E-mag, GPS, contact

Velocity Doppler, Hall effect, optoelectronic

Angular velocity Optical encoder

Acceleration Piezoresistive, piezoelectric,

(9)

Sensors

Measurand Transduction

Contact Strain Piezoresistive

Force Piezoelectric, piezoresistive

Torque Piezoresistive, optoelectronic

Vibration Piezoresistive, piezoelectric, optical fiber, sound,

ultrasound

(10)

Sensors

Measurand Transduction

Presence Tactile Contact switch, capacitive

Proximity Hall effect, capacitive, magnetic, seismic, acoustic,

RF

Distance E-mag (sonar, radar, lidar), magnetic, tunelling

Motion E-mag, IR, acoustic, seismic

(11)

Sensors

Measurand Transduction

Biochemical Agents biochemical transduction

Identification Personal

features Vision

Personal ID Fingerprints, retinal scan, voice, heat plume, vision,

motion analysis

(12)

Sensor Node

Operating System

• TinyOS concepts

• Scheduler + Graph of components

• Component

• Constrained storage model

• Very Lean multithreading

• Efficient Layering

(13)

TinyOS Application

Route Map Router Sensor Application

Active Messages

Radio Packet

Serial

Packet Temp Photo

Radio Byte

UART ADC Clock

RFM

Application

Packet Byte

Bit

(14)

Programming TinyOS

• TinyOS is written in NesC

• Applications are written as system components

• Syntax for concurrency and storage model

• Compositional support

• Separation of definition and linkage

(15)

Simulating TinyOS

• Target platform: TOSSIM

• Native instruction set

• Event driven execution mapped to event drivent simulator

• Storage model mapped to virtual nodes

• Radio and environmental models

(16)

Overview

(17)

Issues and Solutions

• Localization

• Routing

• Medium Access Control

• Applications

(18)

Localization

(19)

Localization

• Fine-grained

• Timing

• Signal strength

• Signal pattern matching

• Directionality

• Coarse-grained

(20)

Triangulation

(21)

Triangulation

A B

C

distance

a b

(22)

Triangulation

C

distance

(23)

Trilateration

(24)

Trilateration

r 1

(25)

Trilateration

r 1

r 2

(26)

Trilateration

r 1

r 2

r 3

(27)

Trilateration

r 1

r 2

r 3

d

(28)

Trilateration

r 1

r 2

r 3

d

j

(29)

Trilateration

r 1

r 2

r 3

d j

i

(30)

Trilateration

r 1

r 2

r 3

d j

i

r 1 2 = x 2 + y 2 + z 2

(31)

Trilateration

r 1

r 2

r 3

d j

i

r 1 2 = x 2 + y 2 + z 2

r 2 2 = (x − d) 2 + y 2 + z 2

(32)

Trilateration

r 1

r 2

r 3

d j

i

r 1 2 = x 2 + y 2 + z 2

r 3 2 = (x − i) 2 + (y − j ) 2 + z 2

r 2 2 = (x − d) 2 + y 2 + z 2

(33)

Trilateration

r 1

r 2

r 3

d j

i

(34)

Trilateration

r 1

r 2

r 3

d j

i

x = r 1 2 − r 2 2 + d 2

2d

(35)

Trilateration

r 1

r 2

r 3

d j

i

x = r 1 2 − r 2 2 + d 2 2d

y = r 1 2 − r 3 2 + (x − i) 2

2j + j

2 + x 2

2j

(36)

Trilateration

r 1

r 2

r 3

d j

i

x = r 1 2 − r 2 2 + d 2 2d

y = r 1 2 − r 3 2 + (x − i) 2

2j + j

2 + x 2

� 2j

(37)

Centroid

(38)

Centroid

(39)

Centroid

(X est , Y est ) = ( X 1 + X 2 + X 3

3 , Y 1 + Y 2 + Y 3

3 )

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